11 dev. integumentary system 2
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The integumentary system consists of skin and its derivatives. The skin is composed of two layers - the epidermis derived from ectoderm and the dermis from mesoderm. During development, the epidermis forms from surface ectoderm and develops layers including the basal layer. Hair, sweat glands, sebaceous glands develop from epithelial thickenings that grow into the dermis. Nails develop from thickened epidermis at digit tips. Mammary glands form from ectodermal ridges along the chest that later develop ducts and connective tissue. The integumentary system fully develops before and after birth to protect and regulate the body.
11 dev. integumentary system 2
- 1. Development of integumentary system Abdurrahman said Hassan
- 2. the integumentary system Human skin is outer covering of the body. In humans largest organ of integumentary system is skin. It guards the underlying: Muscles Bones Ligaments and Internal organs
- 3. the integumentary system Consists of skin & Its derivatives: Sweat glands Sebaceous glands Arrector pili muscles Nails Hair Mammary glands
- 4. Development of skin Skin consists of two layerstwo layers that are derived from two different germ layers EpidermisEpidermis, superficial epithelial tissue derived from surface ectoderm.surface ectoderm. DermisDermis, deeper layer of connective tissue derived from the mesoderm.mesoderm.
- 5. epiDermis In the 4-5th week4-5th week, the skin of the embryo consists of simple cuboidal epithelium….the surface ectoderm By the 7th week7th week, the surface ectodermal cells proliferate and form a layer of squamous epithelium, the peridermperiderm (epitichium) and a basal germinative layer.basal germinative layer. During 11stst & 2& 2ndnd trimesterstrimesters, epidermal growth occurs in stages, which result in an increase in epidermal thickness
- 6. Basal germinative layer This layer becomes the germinativegerminative of the epidermis It proliferates and the new cells are displaced into the layers superficial to it. By 1111thth weekweek, an intermediate layerintermediate layer, containing several cell layers, is interposed between the basal cells and the periderm.
- 7. periDerm The peridermal cells usually cast of during the second part of uterine life, . 3rd month of development epiderms is invaded by cells comes from neural crest to form melanin pigment in milanasomes. Melanasomes are transported down and transferred keratinocytes of the skin and hair bulbs
- 8. Melanoblasts & Melanocytes During the early fetal period the epidermis is invaded by melanoblastsmelanoblasts, cells of the neural crest origin. Melanoblasts move to dermoepidermal junctiondermoepidermal junction and differentiate into melanocytesmelanocytes
- 9. cont’d The cell bodiescell bodies of melanocytes are confined to the basal layersbasal layers of the epidermis, and their processes extend between the epidermal cells. The melanocytes begin producing melaninmelanin before birthbefore birth and distribute it to the epidermal cells.
- 11. derMis The dermisdermis is derived from the mesenchyme underlying the surface ectoderm This mesenchyme is derived from the: Lateral plate mesoderm supplying dermis of upper limb and body wall Paraxial mesoderm which supplies dermis of the back Neural crest supplies dermis of the face and neck By 1111thth weekweek, the mesenchymal cells begin to produce collagenous and elastic connective tissue fibers During the 4th month tissue called corium forms many irregular papillae structures
- 12. derMal PaPillae As the epidermal ridges are formed, the dermis projects upward into the epidermis and forms the dermaldermal papillae.papillae. Capillary loops and sensory nerve endings develop in these papillae. DP DP
- 13. Hair Begin to develop during the 3rd3rd monthmonth, but they do not become visible until the 2020thth weekweek Begins as an epidermal proliferation, the hair budhair bud, into the underlying dermis. The deepest part of the hair bud becomes cup-shaped, forming a hairhair bulb.bulb. The hair bulb gets invaginated by mesenchymal hair papilla.hair papilla.
- 14. Hair cont’d The centralcentral epithelial cells of the hair bulb give rise to the shaft of the hair,hair, that grows through the epidermis and protrudes above the surface of the skin. The peripheralperipheral cells of the hair bulb form the epithelial root sheathepithelial root sheath. The cells of the epithelial root sheath proliferate to form a sebaceous glandsebaceous gland budbud.
- 15. Hair cont’d Surrounding mesenchymal cells differentiate into dermal root sheathdermal root sheath. The arrector pili musclearrector pili muscle differentiates from the surrounding mesenchyme. Continuous proliferation of epithelial cells pushes hair up word. 3rd month first hair appears.
- 16. Hair cont’d Hairs are first recognizable in the region of eyebrows, upper lip and chineyebrows, upper lip and chin The first set of hairs that appear are fine and colorless and are called ‘lanugo’‘lanugo’ hair Lanugo hair are replaced during the perinatal periodperinatal period by coarser hair
- 18. sweat Glands Develop at about 20 weeks20 weeks as solid growth of epidermal cellsepidermal cells into the underlying dermis Its terminal part coilscoils and forms the body of the glandbody of the gland The central cellscentral cells degenerate to form the lumen of the glandlumen of the gland The peripheral cellsperipheral cells differentiate into secretory cellssecretory cells and contractilecontractile myoepithelial cellsmyoepithelial cells
- 19. cont.. There are two types of sweat glands: eccrine glands: Also called marocrine glands, package their secretions in structures called secretory vesicles which travel to the apical surface of the glandular cell and release their secretion by exocytosis Apocrine glands:Secretion occurs with the “decapitation” of the apical surface of the cell and the subsequent release of secretory product and some cellular fragments.
- 20. Vernix caseosa Vernix caseosaVernix caseosa, is the waxy or cheesy white substance found coating the skin of the newborn. The vernix is secreted by the sebaceous glands around the 20th week of gestation It is composed of: SebumSebum (the secretion of the sebaceous glands) Desquamated epithelial cellsDesquamated epithelial cells Fetal hair (lanugo hair)Fetal hair (lanugo hair) It protects the baby's skin from dehydration and from constant exposure to the amniotic fluid.
- 21. nails Begin to develop at about 10th week10th week of gestation, as thickened areas of the epidermis at the tips of the digits.tips of the digits. Later, these nail fields extend to the dorsal surfacedorsal surface and become surrounded by the nail foldsnail folds. Cells from the proximal nail foldproximal nail fold grow over the nail field and form keratinizedkeratinized nail platenail plate, the primordium of the nail.
- 22. The MaMMary Glands Begin to develop during the 6th week6th week as thickened strips of the ectodermectoderm (mammary ridgesmammary ridges) that extend from the axillary to the inguinal regions. They regressregress in most locations exceptexcept in the area of the pectoral musclein the area of the pectoral muscle, where they proliferate.
- 23. The MaMMary Glands conT’d The down growth of epithelial tissueepithelial tissue continues to proliferate into 16 to 24 solid out buddings which give rise to the lactiferous ducts.lactiferous ducts. Fibrous connective tissue and fat of the mammary gland develop from the surrounding mesenchymemesenchyme The lactiferous ducts at first open into a small mammarymammary pitpit.
- 24. PosTnaTal develoPMenT A.A. NewbornNewborn (nipple is inverted) B.B. ChildChild (nipple elevates to form the usual nipple) C.C. PubertyPuberty (breast enlarges due to development of the mammary glands) & deposition of fat D.D. Late pubertyLate puberty E.E. Young adultYoung adult F.F. Pregnant femalePregnant female
- 25. anoMalies • Polymestia • Polythelia • Inverted nipples